diff --git a/Ext4Crypt.h b/Ext4Crypt.h
index ed8bf28..a363d39 100644
--- a/Ext4Crypt.h
+++ b/Ext4Crypt.h
@@ -38,7 +38,7 @@
                       const char* value);
 int e4crypt_set_user_crypto_policies(const char *path);
 
-int e4crypt_create_user_key(userid_t user_id, bool ephemeral);
+int e4crypt_create_user_key(userid_t user_id, int serial, bool ephemeral);
 int e4crypt_destroy_user_key(userid_t user_id);
 
 int e4crypt_unlock_user_key(userid_t user_id, const char* token);